In large commercial sheet fed printers, a stack of sheets of paper or other printable substrate held in the printer's feed unit may weigh more than 100 kilograms. It is desirable to minimize the number of times a heavy sheet stack must be unloaded from the feed unit and reloaded into the feed unit, for example to accommodate the use of a different size or type substrate for an interim print job.
The same part numbers are used to designate the same or similar parts throughout the figures.